1. Field Of The Invention
This invention relates to a tool ball pad hole positioner and, more particularly, to a method and apparatus for drilling a precisely positioned hole in a tool ball pad attached to a tool jig
2. Description Of The Background Art
A tool jig is a device used to position and hold workpieces during machining operations such as drilling, cutting or the like and to guide a tool for such machining operations. A jig may also be used to position many parts to create an assembly. The jig is provided with critically located part index holes and with abutment surfaces in order to effect the positioning of such workpieces. If the holes and abutment surfaces of the jig are not located properly, the workpieces produced in such jig will not meet their engineering design requirements.
The process of providing holes on jigs is normally effected through a tool ball pad with a preformed hole coupleable to the jig. After the tool ball pad has been properly positioned, c-clamps secure the pad in position on the jig while drilling the pad-to-jig attachment apertures. Skilled manpower normally use hammers to tap the pad into position prior to drilling for attachment. This is an inefficient use of skilled manpower and is not time effective or overly accurate. Unfortunately, this procedure has been standard practice in the fabrication of the majority of master and assembly tools throughout the commercial and military aircraft industries. On the average, the entire process to locate and attach the pad to a jig, within plus or minus 0.001 inches in two axes, takes from two to two and a half hours. A typical master jig will require between four and six tool pads while an average assembly jig will utilize a dozen or more of such pads.
A tool ball pad is a hardened steel rectangular block generally measuring two by two and a half by one-half inches with an 0.250 inch diameter through hole in its center. This standard piece of hardware is commonly used during the fabrication of a jig to establish a reference system. The pad, with its 0.250 inch hole located at the center, is positioned on the jig. A target, such as a tooling ball or a theodolite target, is placed in the hole and the pad is moved to position the target to the intended predetermined location shown on the tool design. The position of the target is determined using conventional optics or computer aided theodolites. When the desired position of the hole is obtained, the pad is clamped to the rough surface of the jig. Attachment apertures are drilled and tapped through the corners of the pad into the rough structure of the jig. Fasteners and pins are then installed rendering the pad secure to the jig with the hole of the pad in the proper location on the jig.
Problems exist with the present method since it is difficult to clamp the pad securely to the rough structure of the jig in a fashion which prevents inadvertent movement while allowing for intentional movement during positioning of the pad and hole. Another problem is moving the pad a precise amount in one axis without affecting its position in the other axis. The presently utilized industry method requires striking a hammer against the tool ball pad with an educated amount of force and direction to produce the desired result. To be expeditious, this practice requires experience.
Another presently encountered problem is obtaining sufficient clamping pressure to prevent inadvertent movement of the tool pad during drilling and tapping of the jig In addition, inadvertent movement between pad and jig often occurs during the application of the clamping forces. Further, irregularities o the surface of jig where the pad is attached causes displacement of the pad as it is being tightened down.
Lastly, the depth of the attachment apertures in tool ball pads presently available to guide the drill is merely 0.125 inches due to a 0.375 inch deep counter bore for the bolt head. This depth is inadequate if drilled holes, concentric with the center line of the pad holes, are going to be produced. If concentricity is not maintained, the bolts will thread into the pad and jig structure at an angle and change the position of the pad as it is being tightened down. Presently, only skilled mechanics are capable of producing holes in the jig that are concentric with the holes in the pads.
Various approaches are disclosed in the patent literature for the positioning of one part with respect to another. Note, for example, U.S. Pat. No. 3,775,857 to Handy and U.S. Pat. No. 4,425,076 to Colineau. Neither of these patents, however, are capable for use in drilling holes in a jig through a tool ball pad hole positioner as contemplated herein. The patent to Handy discloses a tool intended to be used to simplify the indexing of materials to be machined on a numerically controlled machine tool. It offers no provision to locate a tool ball pad hole positioner and an optical target in the manufacturing of jigs The patent to Colineau has, for its purpose, the arcuate positioning and securement of electrical components to a work table during the assembly of an electrical circuit. Thus, it cannot aid in the positioning and securing of a tool ball pad hole positioner to the rough structure of a jig.
As illustrated by a large number of prior patents and commercial devices, efforts are continuously being made in an attempt to improve apparatus and methods for positioning one component with respect to the other. Such efforts are being made to render such positioning more efficient, reliable, inexpensive and convenient to use. None of these previous efforts, however, provides the benefits attendant with the present invention. Additionally, the prior patents and commercial devices do not suggest the present inventive combination of method steps and component elements arranged and configured as disclosed and claimed herein. The present invention achieves its intended purposes, objects and advantages through a new, useful and unobvious combination of method steps and component elements, with the use of a minimum number of functioning parts, at a reasonable cost to manufacture and use, and by employing only readily available materials.
Therefore, it is an object of this invention to provide an improved tool ball pad hole positioner which comprises a first plate which is securely positionable with respect to a jig and has a large aperture therein; a second. plate which is movable with respect to the first plate and has a small circular aperture therein over lying the large aperture; a target which is removably receivable within the small aperture and able to be sighted by an optical device for determining the precise location of the target as well a the aperture with respect to the precise location on the jig; means to positively secure the first plate to the jig; means to shift the second plate with respect to the first plate and means to releasably clamp the second plate with respect to the first plate.
It is a further object of this invention to provide an improved method of drilling a hole in a tool ball pad blank secured to a jig at a precise predetermined location as by the above described apparatus.
It is yet a further object of this invention to drill holes in tool ball pads positively secured to jigs at precise positions through improved tool ball pad hole positioners.
Lastly, it is an object of the present invention to accurately shift an aperture in a tool ball pad hole positioner in order to locate a predetermined location for a hole to be drilled.
The foregoing decision outlines some of the more pertinent objects of the invention. These objects should be construed as merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.